Hydraulic System for Control of Power Windmills
Clean Technology 2008

Hydraulic System for Control of Power Windmills

A. Sanderson
Sanderson Engine Development Company, US

wind turbine variable speed hydraulic

A recently invented axial mechanism called the Sanderson Rocker Arm Mechanism, or SRAM, converts rotary to reciprocating motion almost without loss in both directions, Figure 1. The main improvement is due to the almost total elimination of side load in the piston-to-cylinder interface, with a rocker-arm connection instead of a slider-crank connection. The usual hydraulic mechanisms rely totally on side load to support the torque of the rotating shaft, which leads to high friction, to slip-stick and low-rpm chaotic behavior. The torque of an SRAM device is supported entirely by a universal joint, grounded on one side. Because of straight-line motion of SRAM pistons in cylinders, the overall efficiency is very high with both hydraulic motors and hydraulic pumps. Torque efficiency holds up down to zero rpm, and volumetric efficiency down to a few rpm. The SRAM also eliminates the troublesome issues of slip-stick start and erratic performance below 500 rpm, that prevents their use in low-speed applications such as power windmills, for example. This paper examines new applications of hydraulics to wind power that have become highly feasible with SRAM pumps and motors.